SNVSC78D February   2022  – September 2026 LMQ66410 , LMQ66420 , LMQ66430

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 System Characteristics
    7. 6.7 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Enable, Start-Up, and Shutdown
      2. 7.3.2  Adjustable Switching Frequency (With RT)
      3. 7.3.3  Power-Good Output Operation
      4. 7.3.4  Internal LDO, VCC, and VOUT/FB Input
      5. 7.3.5  Bootstrap Voltage and VBOOT-UVLO (BOOT Terminal)
      6. 7.3.6  Output Voltage Selection
      7. 7.3.7  Spread Spectrum
      8. 7.3.8  Soft Start and Recovery from Dropout
        1. 7.3.8.1 Recovery From Dropout
      9. 7.3.9  Current Limit and Short Circuit
      10. 7.3.10 Thermal Shutdown
      11. 7.3.11 Input Supply Current
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Standby Mode
      3. 7.4.3 Active Mode
        1. 7.4.3.1 CCM Mode
        2. 7.4.3.2 Auto Mode – Light Load Operation
          1. 7.4.3.2.1 Diode Emulation
          2. 7.4.3.2.2 Frequency Reduction
        3. 7.4.3.3 FPWM Mode – Light Load Operation
        4. 7.4.3.4 Minimum On-Time (High Input Voltage) Operation
        5. 7.4.3.5 Dropout
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Synchronous Buck Regulator at 400kHz
      2. 8.2.2 Design Requirements
      3. 8.2.3 Detailed Design Procedure
        1. 8.2.3.1  Choosing the Switching Frequency
        2. 8.2.3.2  Setting the Output Voltage
          1. 8.2.3.2.1 VOUT / FB for Adjustable Output
        3. 8.2.3.3  Inductor Selection
        4. 8.2.3.4  Output Capacitor Selection
        5. 8.2.3.5  Input Capacitor Selection
        6. 8.2.3.6  CBOOT
        7. 8.2.3.7  VCC
        8. 8.2.3.8  CFF Selection
        9. 8.2.3.9  External UVLO
        10. 8.2.3.10 Maximum Ambient Temperature
      4. 8.2.4 Application Curves
    3. 8.3 Best Design Practices
    4. 8.4 Power Supply Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
        1. 8.5.1.1 Ground and Thermal Considerations
      2. 8.5.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Third-Party Products Disclaimer
      2. 9.1.2 Device Nomenclature
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

8.2.3.9 External UVLO

In some cases, an input UVLO level different than that provided internal to the device is needed. This can be accomplished by using the circuit shown in Figure 8-2. The input voltage at which the device turns on is designated as VON while the turn-off voltage is VOFF. First, a value for RENB is chosen in the range of 10kΩ to 100kΩ, then Equation 10 and Equation 11 are used to calculate RENT and VOFF, respectively.

LMQ66410 LMQ66420 LMQ66430 Setup for External UVLO Application Figure 8-2 Setup for External UVLO Application
Equation 10. RENT=VONVEN-VOUT-1×RENB
Equation 11. VOFF=VON×1-VEN-HYSVEN-VOUT

where

  • VON is the VIN turn-on voltage.
  • VOFF is the VIN turn-off voltage.